What determines vegetation on rock outcrops of the Western Ghats: the macro-environment or lithotype?

The northern section of the Western Ghats is a biodiversity hotspot with a predominance of rock outcrops. Although these outcrops are characterized by environmental extremes, they support a large diversity of species, many of which are endemics. High-elevation rock outcrops of the Western Ghats exhibit two lithotypes of distinct geological origins, namely basalt mesa (BM) and high-level ferricrete (HLF). We examined the interrelation between environmental factors, lithotypes and functional type abundance. We recorded 265,447 individuals belonging to 127 taxa categorized under seven plant functional types in 128 quadrats from sixteen high-elevation rock outcrops. Cluster analysis separated the sites based on the lithotypes. Graminoids and Therophytes were the dominant functional types across both the lithotypes. Latitude, seasonality, soil carbon and nitrogen were the influential environmental factors. Multivariate analysis of variance (MANOVA) showed that based on environmental characteristics, the two lithotypes are significantly different from each other. Different plant functional types were associated with different environmental variables, as shown by canonical correspondence analysis (CCA). Lithotype and levels of soil carbon and nitrogen together seem to shape the functional type abundance. Overall, we observed that there is a marginal difference in the vegetation across the two lithotypes of outcrops. The abundance of each plant functional type was deferentially associated with the seasonal environment and soil nutrients.